Benzo(B)Thiophene-2-Boronic Acid → 2-(2-Pyridyl)benzothiophene

Participants

Reaction Steps

A two-necked 250 mL round-bottomed flask fitted with a reflux condenser (with gas inlet) and a rubber septum was flushed with argon before 2-bromopyridine (2.57 mL, 27 mmol) and ethyleneglycol dimethylether (80 mL, dry and degassed) were introduced. Tetrakis(triphenylphosphine)palladium (1.0 g, 0.87 mmol) was added and the solution stirred at room temperature for 10 minutes. Benzothiophene-2-boronic acid (5.0 g, 28.1 mmol) was then added, followed by anhydrous sodium bicarbonate (8.4 g. 100 mmol) and water (50 mL, degassed). The septum was replaced with a glass stopper and the reaction mixture was heated at 80° C. for 16 hours, cooled to room temperature and the volatiles removed in vacuo. Organics were extracted with ethyl acetate (3×100 mL), washed with brine and dried over magnesium sulfate. Removal of the organics yielded a pale yellow solid. Recrystallisation from ethanol yielded a colourless solid (3.9 g, 68%, two crops), m.p. 124-6° C.

Provenance & Evidence